Two different processes are known for depositing hard-material particles together with the matrix material, on component areas to be protected. In a first known process the hard-material particles are loaded into a plasma torch together with the matrix metal and are sprayed onto the component in the plasma beam or stream. The first process has the disadvantage that in the hot plasma stream, sharp edges of the hard-material particles may be lost because particle points, edges and burrs become plasticized or blunted by fusion with other particles. Another disadvantage of the first known method is caused by the difficulty to properly meter and uniformly distribute the hard-material particles. A high input or dose of hard-metal particles, e.g., causes the particles to collide on the component surface with one another, so that the particles bounce back into the plasma stream and form matrix holes on their underside when reimpinging on the component surface. As a result the anchorage of the particles in the matrix is minimal and it takes little wear to make them work loose from the matrix metal. The particles may also agglomerate in the matrix metal, whereby their uniform distribution throughout the matrix material is not assured.
In order to prevent the hard-material particles becoming blunt along particle edges by fusion, the second known coating technique resorts to sprinkling the hard-material particles under the action of gravity onto the surface in the area where the plasma stream applies the matrix material to the component surface. The second known technique has the disadvantage that the hard-material particles sprinkled onto or into the coating area fall on an already solidified matrix metal surface and are covered with matrix metal by the plasma stream, so that the hard-material particles will not be anchored in the matrix metal at the particle underside. Worse yet, pores may partially form on the particle underside. Such hard-material particles which are loose at their underside, may, under centrifugal load on the coating, cause a partial or complete detachment of the dispersion coating, especially in areas where hard-material particles sprinkled onto or into the coating area have agglomerated. Additionally, the hard-material particles may prematurely detach from the metal matrix, because their underside is not sufficiently anchored to the matrix metal.